Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
346 AM EDT Wed Apr 24 2024

Valid 12Z Wed Apr 24 2024 - 12Z Sat Apr 27 2024

...Northern Maine...
Day 1...

A potent shortwave trough traversing the Northeast today will help
to spawn a wave of low pressure in eastern Quebec this afternoon
while rapid cooling on the western flank of the developing area of
low pressure results in a brief burst of moderate snowfall. Latest
forecast calls for generally 1-3" in northern Maine, but given WPC
PWPF shows low chances (10-30%) of snowfall totals >4" west of
Caribou, localized amounts topping 4" cannot be ruled out. Snow
will quickly end Wednesday evening with an unusually cold day late
April day to follow on Thursday.

...The West...
Days 1-3...

A series of upper level disturbances will carve out a broad
longwave trough across the western U.S. that will be responsible
for some late season mountain snowfall from the Cascades and Sierra
Nevada to as far east as the Colorado Rockies. The initial 500mb
disturbance approaching southern California will be responsible for
a burst of heavy snow over the White Mountains along the CA/NV
border today and into this evening. Mountain snow will then pick
up over the Four Corners region by Thursday afternoon as the same
upper trough moves in overhead. Farther north, the next upper
level trough looks to amplify over the Pacific Northwest Thursday
evening. While the lead disturbance over the Four Corners region
will generate some high elevation snow >9,000ft in the Colorado
Rockies through Thursday night, it is the trough along the West
Coast that will be the primary driver in mountain snow Friday and
into the upcoming weekend. By Friday morning, falling 700-500mb
heights over the Intermountain West and a surge in Pacific moisture
allows for more snow to breakout across many mountain ranges that
include the Blue Mountains, the Sawtooth, Absaroka, Tetons, Wind
River, Big Horns, central Great Basin, and the Uinta. By Friday
night, the heaviest snowfall rates are anticipated in the Absaroka
and Wind River Ranges where 500-700mb winds out of the southeast
will lead to additional upslope enhancement in these ranges. These
ranges will remain favored for the heaviest snowfall into Saturday
morning as the 500mb low tracks over the Colorado Rockies.

WPC PWPF shows high chances (>70%) for snowfall totals >8" in the
Sawtooth
of central Idaho, the Absaroka, Wind River Range, and both the
Wasatch and Uinta ranges, all at elevations >9,000ft. The Wind
River Range in western Wyoming sports moderate chances (40-60%) for
snowfall totals >12" through Saturday morning. Note that
additional snowfall is still not over in the Absaroka and the Wind
River Range through Saturday afternoon as the upper trough deepens
over the Four Corners region and spawns a surface low in lee of the
Colorado Front Range on Saturday.


The probability of significant icing is less than 10 percent.


Mullinax